The present invention refers to a method of reinforcing sheet metal panels, shaped plastic panels or the like, by means of an essentially flat stiffening member consisting of one or more layers, said stiffening member including at least one layer which consists at least partially of a thermosetting resin. Further, the invention refers to an essentially flat stiffening member having one or more layers usable to perform the method of the invention, said stiffening member including at least one layer which consists at least partially of a thermosetting resin.
According to the known prior art, multi-layer stiffening members may be used to reinforce a sheet metal panel, a shaped plastic panel or the like, e.g. a portion of a body of an automobile, which comprise a first, fibre-reinforced layer, e.g. a glass fibre tissue impregnated with a thermosetting resin material, this layer constituting the real stiffening layer. One surface thereof usually is coated with a second layer consisting of a further, thermosetting resin, said second layer serving as an adhesive layer.
A multi-layer stiffening member of this kind may be used to reinforce flat or curved panels like, for instance, sheet metal portions by placing a piece of the multi-layer stiffening member with its sticky resin surface onto the sheet metal portion to be reinforced and subsequently subjecting it to a heat treatment. Thereby, on the one side, an adhesion of the multi-layer stiffening member to the sheet metal portion is effected and, on the other side, the resin layers are cured such that a stiff connection between the sheet metal portion and the fibre reinforced layer results. In this way, an essential stiffening of the sheet metal portion may be achieved in a very simple manner without the disadvantage of substantially increasing the weight of the panel to be reinforced.
In order to ensure that the multi-layer stiffening member can easily be applied to the sheet metal portion to be reinforced, the adhesive resin layer usually has a sticky surface such that the applied mult-layer stiffening member adheres in the required position on the sheet metal portion until it is subjected to a heat treatment. However, one is forced to protect the sticky resin surface of the multi-layer stiffening member until it is used in order to protect the sticky resin surface from contamination and, further, in order to enable a plurality of multi-layer stiffening members to be stacked. In the prior art, such protection is in the form of a suitably treated paper sheet or a protection foil which can be removed from the multi-layer stiffening member surface immediately prior to its application.
One of the most important disadvantages thereby is that the removal of the protection paper or the protection foil is an undesired additional operation step which hardly can be performed automatically. Particularly, in the field of automobile construction in which such multi-layer stiffening members are widely used and in which an important goal consists in the automation of as many operation steps as possible, this operation of removing the protection paper or the protection foil is considered as an undesired and time-consuming job which can be performed only by a human operator.